Resistance-Temperature “Scaling” of Carbon-Composition Thermometers
For several years, Allen-Bradley carbon-composition resistors have been used at low temperatures as secondary thermometers.1 We have recently been considering the possibility that the calibration of each such resistor may be specified by two scaling parameters, R0 and T0, such that R/R0 is a universal function of T/T0, This possibility was suggested by the fact that, for different resistors, plots on logarithmic scales of resistance as a function of temperature could be very nearly superposed by a simple translation of the axes of one graph relative to those of another. Figure 1 shows measurements on ten resistors when plotted in this way. The choice of origin on such a graph is arbitrary, and we have chosen it so that R0 and T0 are unity for a 33 ohm, 1 watt resistor. Table 1 lists R/R0 and T/T0 for a smooth curve passing through the points in Figure 1. Except for a few points at room temperature and liquid nitrogen temperatures, the data scatter about this curve by one or two per cent in resistance.
KeywordsUniversal Function Logarithmic Plot Liquid Helium Temperature Normal Boiling Point Simple Translation
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